Manufacture of compound ingots.



No. 638,908. Patented Dec. I2, I899;

, S. A. COSGRAVE.

MANUFACTURE OF COMPOUND INGOTS.

(Application flied Sept. 1, 1899.) (No Model) 2 Shuts-Sheet I.

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HA AuSM No. e3a,9os. Patented Dec. 12, I899.

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MANUFACTURE OF COMPOUND INGOTS.

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NITE TATES PATENT rrrcn.

SYLVESTER A. COSGRAVE, OF EDGEVVOOD PARK, PENNSYLVANIA, ASSIGNOR TO MARIA l3. COSGRAVE, OF SAME PLACE, AND AARON FRENCH AND MARGARET L. PATTERSON, OF PITTSBURG, PENNSYLVANIA,

MANUFACTURE OF COMPOUND INGOTS.

SPECIFICATION formingpart of Letters Patent No. 638,908, dated December 12, 1899.

Application filed September 1, 1899.

T ctZZ whom it may concern:

Be it known that I, SYLVESTER A. Cos- GRAVE, a citizen of the United States, residing at Edgewood Park, in the county of Allegheny and State of Pennsylvania, have invented or discovered certain new and useful Improveinents in the Manufacture of Compound Ingots, of which improvements the following is a specification.

The invention described herein relates to certain improvements in the manufacture of compound ingots. Many methods have been proposed for the purpose, but have been practically unsuccessful Where the compound I 5 plate is subjected to heavy strains or severe shocks, as the impact of projectiles. It is characteristic of the methods heretofore employed that there is a sharp line of demarcation between the two grades of metal, so that It is characteristic of armor-plates having their exposed faces hardened by recarburizing or otherwise that the hardened portions will not break off even when subjected to the severest shocks. This characteristic is, I believe, due to the fact that there is a gradual change from one kind or grade of metal to the other, so that no plane or line of cleavage is formed.

The object of the present invention is to 0 provide for the casting of one metal on the other under such conditions as will permit or facilitate the" modifying or changing of the characteristics of one body of metal by those of the other, so that there will be a gradual 3 5 change in character, as from high to low carbon from one plate to the other.

In the accompanying drawings, forming a part of this specification, Figure 1 is a sectional elevation of a mold having a transverse 4o partition, the space on one side of the partition being filled with metal. Fig. 2 is a sectional elevation of a mold with a core in position and one of the metals cast around the core, and Fig. 3 is a similar view illustrating a modification in the construction of the mold and in the manner of filling the mold.

The invention consists in bringing together two bodies of molten metal on opposite sides of a wall or diaphragm formed of metal of the same character as one of the bodies and being Serial No. '729163- (No specimens.)

heated to such a temperature that it will not have any material cooling action on either body, but will become molten almost instantaneously when inclosed by the two molten bodies. This method can be effected by pouring one of the metals in a mold, as 1, having a removable core 2, as shown in Figs. 2 and 3, or having a removable partition 3, as shown in Fig. 1. As soon as the metal in contact with the core or partition has solidified sufficiently to restrain the molten metal in the interior portion the core or partition is withdrawn and the other metal poured. into the mold. It is preferred, as shown in Fig. 3 and as specifically set forth in application Serial No. 729,164, filed September 1, 1899, to construct the mold so that the second body of metal may enter through the bottom of the mold, so that the metal will as nearly as practicable follow up the core or partition as it is withdrawn, thereby avoiding to a great ex tent any exposure of the surface of the metal first cast to atmospheric influences. As a general practice it is preferred to form the core or partition of or to coat the same with some material which will either prevent such elemental changes of the metal in contact therewith as would tend to prevent a union or mixture of the metals or will, in case such changes should occur, effect a reconversion or elimination of the portions of metal so changed. These ends can be attained either by forming the core or partition of or coating them, as at 0;, with a fiuxing material, as silica, or a deoxidizing material, as carbon. The employment of a fluxing material for the purposes stated forms no part specifically of the invention herein claimed, as such use forms a part of the subject-matter of an application, Serial No. 714,952, filed April 29, 1899.

A desirable method of practicing the invention herein described consists in casting one of the metals, as high-carbon steel, in a suitable mold, and then, while still at a high tem- 9 perature, the surface to which the other metal is to be united is subjected to such treatment as will prevent such elemental changes, as the formation of oxids, &c, which would interfere with an intimate union with the other metal, or, in case such changes have occurred will reconvert the metal to a homogeneous condition. As soon as the surface of the metal has been heated the other metal is cast thereon. This treatment of the surface of the first body of metal should be effected while the metal is in a molten condition or while it is at such a high temperature as to become molten when the other metal is poured thereon.

A convenient manner of practicing my i11- ventien consists in forming that wall of a mold forming the matrix of the surface against which the other metal is to be poured of some suitable material, as carbon, which will prevent the formation of oXids or will reconvert such oxids to a metallic condition. The carbon should be in such condition that it will be readily taken up by the metal in contact therewith, so that each metal will have a considerable amount of graphitic or free carbon mixed therewith. As soon as the metal in contact with the prepared wall has hardened sufficiently to retain the interior metal, such metal being at such time in a molten condition, the mold-wall is removed and the other body of metal, as low-carbon steel, is poured into the mold. The thin molten-metal-retaining shell on the surface of the body of metal first cast will be again fused, asit is at the time of pouring the second body of metal, at a temperature not greatly below its melting-point and lies between two bodies of metal at a temperature considerably above melting-point. As the thin shell of metal and the molten metal of the body first cast adjacent to such shell are saturated with carbon, it follows that when the shell or wall becomes molten there will be a thin stratum of molten metal between the two bodies containing a higher percent-age of carbon than either of these two bodies. As the metal of both bodies is molten, a condition most favorable to the diffusion of the carbon, the carbon in the saturated strata will gradually diffuse, the low-carbon steel taking up the greater proportion thereof. Although the portion of the high-carbon metal adjacent to the other bodyof metal may have a little higher carbon than the remaining port-ions thereof, so that the ingot will contain three strata of metal each varying in carbon content-4. e., stratum containing high percentage of carbon, a comparatively thin stratum containing a'still higher percentage of carbon, and a stratum containingalow percentage of carbonit is still true that there will not be a sharp line of demarcation between the several strata; but there will be a gradual change in carbon content from one stratum to the other.

By way of more carefully setting forth the characteristic features of the present invention it may be stated that in this branch of the art as heretofore practiced the aim of inventors has been to effect a perfect weld or the best attainable weld or union along the meeting faces of the two bodies. This has been done, or, rather, it has been aimed at, in two ways. In one way a solidified crust was produced on one quality or body of metal and the other quality or body of metal was cast onto or against such crust; but the aim in all cases, so far as my knowledge goes, was to make such crust of the proper thickness whereby on its being fused or partially fused the two qualities of metals should be welded together along such plane or fusion or partial fusion; but in every case, so far as my knowledge goes, the two bodies or qualities of metal were kept distinct from each other, except as so welded, and any material or substantial interdiffusion or blending of the qualities of the two metals through each other was either not provided for or was studiously avoided, and in this latter respect, as will presently be explained, the method involved in the present invention differs substantially from the method above stated to be old. In the other old method of uniting different qualitiesor bodies of metal in a compound plate it was customary to interpose between the two bodies a metallic diaphragm of suitable material and the proper thickness, which diaphragm, under the action of the heat of the metals cast thereon on its opposite sides, would become fused, and thereby permitting the formation of a weld betweenlthe two bodies, but, as before,without any material or substantial interditfusion between the different qualities of metal constituting the two bodies.

It is a characteristic feature of the present invention that in the formation of a weld as a weld between two contiguous bodies the metal of different qualities is carefully avoided. My own experience has been that where two qualities of steel characteristically different are united by a weld in such way as to preserve in each body its characteristic and distinctive qualities and without any gradual or decremental merging of the qualities of one body into those of the other a practically homogeneous compound ingot or plate cannot be made. There will always exist in such welded compound ingots or plates a plane of clevage or breakage along which the cohesive properties of the metal will be materially less than in any other part, and so much less that under severe use the plate is liable to be broken or destroyed. In the presentinvention,on the other hand, I aim to avoid the formation of a crust such as is liable to produce what previous inventors have aimed at and by which they have produced a weld or a welded union; but I produce a crust so thin that it will immediately disappear on the pouring in of the additional molten metal, whereby two qualities or grades of molten metal are brought together face to face and in such condition that before complete solidification takes place there will be an interchange of qualities from one to the other such as to result in a gradual merging from the high carbon of the surface to the low carbon of the center and Without any definable or ascertainable plane of clevage therein or any plane marked by a sudden or abrupt change in point of carbonization. Employing a term commonly used in another branch of the art, the compound plate or ingot which I thus produce may fairly be characterized as a plate or ingot decremenially carbonized as distinguished from a compound plate formed by welding together the adjacent surfaces.

I claim herein as my invention 1. The method herein described of making compound ingots, which consists in casting a body of metal in a mold having a movable wall, promptly and progressively removing said wall from the cast metal and bringing another body of molten metal against the surface exposed by the withdrawal of the wall of the metals against a mold-wall consisting of, or formed by, a deoxidizing material and then removing the mold-wall and casting the other metal on the exposed or uncovered surface, While the latter is at high temperature, substantially as set forth.

In testimony whereof I have hereto set my 30 hand.

SYLVESTER A. OOSGRAVE.

Witnesses:

DARWIN S. WoLooTT, M. S. MURPHY. 

